Mobile devices are essentially handheld radios that communicate by exchanging radio signals at defined frequencies with network access points. Mobile devices can gain access to cellular networks via cellular base stations. Mobile devices can gain access to the Internet via wireless Local Area Networks (WLANS) using WiFi access points. WiFi refers to the underlying technology of wireless local area networks (WLAN) based on the IEEE 802.11 specifications. Wi-Fi was originally intended to be used for mobile computing devices, such as laptops, in LANs, but is now often used for increasingly more applications, including Internet access, gaming, and basic connectivity of consumer electronics such as televisions and DVD players. Mobile devices can also gain access to other networks using the WiMAX (802.16) standard wherein a scheduling algorithm is applied to assign a time slot to a subscriber to enable it to communicate with a base station.
The growing rise in handheld devices has increased the demand for wireless network coverage. Because wireless access points have a limited transmission range, providing wireless coverage for an entire building or corporate campus generally requires the integration of multiple wireless local area networks (WLANS) although these provide coverage for a building or campus, cellular networks are still required to provide coverage outside the building or campus. As mobile clients move into or outside the building or campus it is desirable to maintain the continuity of communications even as the clients are transitioned between different wireless networks. One problem with transitioning between networks is that the hand-off of communications is often time consuming, and during the hand-off process the communication may experience interruption, causing frustration for the client. A technique is required to seamlessly transition between wireless networks.